linux-kernel - [PATCH 3.16 088/134] staging: gdm724x: gdm_mux: Remove create

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Date:   Fri, 18 Aug 2017 14:13:20 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org,
        "Amitoj Kaur Chawla" <amitoj1606@...il.com>,
        "Greg Kroah-Hartman" <gregkh@...uxfoundation.org>
Subject: [PATCH 3.16 088/134] staging: gdm724x: gdm_mux: Remove
 create_workqueue()

3.16.47-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Amitoj Kaur Chawla <amitoj1606@...il.com>

commit c272dc2da14cde0bfd9495a5aafb8e3e94f35601 upstream.

With concurrency managed workqueues, use of dedicated workqueues
can be replaced by using system_wq. Drop mux_rx_wq by using system_wq.

Since there is only one work item per mux_dev and different mux_devs
do not need to be ordered, increase of concurrency level by switching
to system_wq should not break anything.

cancel_work_sync() is used to ensure that work is not pending or
executing on any CPU.

Lastly, since all devices are suspended, which shutdowns the work item
before the driver can be unregistered, it is guaranteed that no work
item is pending or executing by the time exit path runs.

Signed-off-by: Amitoj Kaur Chawla <amitoj1606@...il.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/staging/gdm724x/gdm_mux.c | 18 +++---------------
 1 file changed, 3 insertions(+), 15 deletions(-)

--- a/drivers/staging/gdm724x/gdm_mux.c
+++ b/drivers/staging/gdm724x/gdm_mux.c
@@ -26,8 +26,6 @@
 
 #include "gdm_mux.h"
 
-static struct workqueue_struct *mux_rx_wq;
-
 static u16 packet_type[TTY_MAX_COUNT] = {0xF011, 0xF010};
 
 #define USB_DEVICE_CDC_DATA(vid, pid) \
@@ -277,7 +275,7 @@ static void gdm_mux_rcv_complete(struct
 		r->len = r->urb->actual_length;
 		spin_lock_irqsave(&rx->to_host_lock, flags);
 		list_add_tail(&r->to_host_list, &rx->to_host_list);
-		queue_work(mux_rx_wq, &mux_dev->work_rx.work);
+		schedule_work(&mux_dev->work_rx.work);
 		spin_unlock_irqrestore(&rx->to_host_lock, flags);
 	}
 }
@@ -604,6 +602,8 @@ static int gdm_mux_suspend(struct usb_in
 	mux_dev = tty_dev->priv_dev;
 	rx = &mux_dev->rx;
 
+	cancel_work_sync(&mux_dev->work_rx.work);
+
 	if (mux_dev->usb_state != PM_NORMAL) {
 		pr_err("usb suspend - invalid state\n");
 		return -1;
@@ -659,13 +659,6 @@ static struct usb_driver gdm_mux_driver
 
 static int __init gdm_usb_mux_init(void)
 {
-
-	mux_rx_wq = create_workqueue("mux_rx_wq");
-	if (mux_rx_wq == NULL) {
-		pr_err("work queue create fail\n");
-		return -1;
-	}
-
 	register_lte_tty_driver();
 
 	return usb_register(&gdm_mux_driver);
@@ -675,11 +668,6 @@ static void __exit gdm_usb_mux_exit(void
 {
 	unregister_lte_tty_driver();
 
-	if (mux_rx_wq) {
-		flush_workqueue(mux_rx_wq);
-		destroy_workqueue(mux_rx_wq);
-	}
-
 	usb_deregister(&gdm_mux_driver);
 }